cygwin qsort erratic
Thomas Wolff
towo@towo.net
Wed Sep 2 07:23:27 GMT 2020
Am 02.09.2020 um 02:26 schrieb Kurt-Karen Carlson-Lougheed:
> Thomas:
> As stated, twice, the full code is on SourceForge as uac19 v3.3. If
> you need me to send you a tgz with sample data please let me know, but
> note the comments and patch below. I can certainly walk you through
> reproducing the problem if you believe that is worthwhile.
Kurt-Karen:
I am not uac savvy. The proposal to dig out some software package, build
it (which may create hours-long trouble in some cases), collect data
from somewhere else etc, to reproduce an assumed bug, is not
appropriate. It's your term to provide a single, reproducible
demonstration of a bug. If this were an issue in my project, I would
close it now for refusal of cooperation.
>
> Stephen:
> Thank you. I couldn't get the 'blame' to work (I am not git savvy),
> but I got the cygwin qsort.c. The problem is *EXACTLY* as described by
> Dennis de Champeaux in the 2015-01-11 cygwin list posting. The
> secondary insertion sort attempt is not safe. I patched as follows,
> the de Champeaux is code is more correct in removing swap_cnt as it is
> no longer used:
>
> kc: diff -u qsort.c cygsort.c
> --- qsort.c 2020-09-01 15:36:39.716029300 -0700
> +++ cygsort.c 2020-09-01 16:47:30.152545600 -0700
> @@ -252,14 +252,15 @@
> pb += es;
> pc -= es;
> }
> - if (swap_cnt == 0) { /* Switch to insertion sort */
> +/* kc
> + if (swap_cnt == 0) { // Switch to insertion sort
> for (pm = (char *) a + es; pm < (char *) a + n * es;
> pm += es)
> for (pl = pm; pl > (char *) a && CMP(thunk, pl
> - es, pl) > 0;
> pl -= es)
> swap(pl, pl - es);
> goto pop;
> }
> -
> +kc */
> /*
> * Rearrange the array in three parts sorted like this:
> * { elements < pivot, elements == pivot, elements > pivot }
>
> If you need me to provide further information, please advise.
> Regards, kurt
>
> On Tue, Sep 1, 2020 at 3:02 PM Thomas Wolff <towo@towo.net
> <mailto:towo@towo.net>> wrote:
>
> Am 01.09.2020 um 22:29 schrieb Kurt-Karen Carlson-Lougheed via Cygwin:
> > Brian:
> > 1. The Qsort() source I sent was from netbsd.org
> <http://netbsd.org>, NOT cygwin. netbsd works.
> > 2. Complete package is on SourceForge as uac19 v3.3. I'm happy
> to send a
> > tgz if you prefer that. Read 3 choices at end before considering
> this.
> > 3. Data is curl'd from owid as shown in the script example.
> Likewise I can
> > send a sample data set. The program analyzes COVID-19 csv files
> from either
> > owid or github/nytimes
> > 4. I've used qsort() for years. I agree, keeping the sort
> routines simple
> > is always appropriate. I confirmed today the only ones that fail
> include
> > float divides, lDsort() and lXsort() in attached c19sort.c. When
> it's
> > pre-calculated and added to the struct it works, the code has a
> toggle now
> > for testing that.
> >
> > Thomas:
> > I tried (again) today to build a simple test case. The data
> structures in
> > use are complex, probably the only thing I can attempt is
> stripping down
> > the code which will be very time consuming. I know you don't
> know me at
> > all, but I've written code, debugged proprietary operating systems
> > (assembler), performed OS dump analysis, troubleshot
> intermittent hardware
> > issues, identified disk firmware issues causing intermittent data
> > corruption, identified nfs performance issues, managed large hpc
> clusters,
> > etc. etc. etc. over 40+ years.
> Your code does not even compile. I did not ask for a minimal test
> case
> although that is generally appreciated. But a working test case at
> least
> is required to establlish your claim of a bug.
> >
> > I see three choices:
> > A. One of you look at simple the qqsort wrapper. I modified my
> code to
> > toggle between the functional netbsd Qsort() and cygwin qsort().
> I have
> > demonstrated erroneous results coming from the cygwin version in
> a small
> > percentage of requests. If you can acknowledge that, perhaps you
> can check
> > the cygwin version of qsort() vs. the current netbsd.org
> <http://netbsd.org>?
> > B. If you could kindly provide me or point me to the cygwin
> qsort() source
> > I'll check it out myself.
> > C. We can thank each other and leave cygwin's qsort() as is
> broken in some
> > small number of circumstances since I've compiled netbsd's into
> my code and
> > that always works.
> >
> > Regards, kurt
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